async fn process_graph(graph: &Graph) -> Vec<usize> {  
    let mut result = vec![];  
    // TODO: 异步遍历图节点  
    result  
}  

#[test]  
fn test_async_graph() {  
    let rt = tokio::runtime::Runtime::new().unwrap();  
    let graph = Graph::new(5);  
    rt.block_on(async {  
        assert!(!process_graph(&graph).await.is_empty());  
    });  
}  